Patent GB-770963-A (GB)
Title: Focal plane shutter
IPC: G03B9/42
Filed: 1954-10-15
Abstract: 770,963. Photographic shutters. BERGERHOFF, H. Oct. 15, 1954 [Oct. 30, 1953], No. 29779/54. Class 98(1) A focal plane shutter with bulb and instantaneous exposures has leader and follower shutter plates which move in the same direction, each with actuating means connected to a common drive member, the actuating means for the follower shutter plate comprising an element which, at the commencement of release of the shutter, yields, until arrested by a stop so that the element then drives the follower shutter plate, the position of the stop being adjustable to vary the instant of operation of the follower plate and give an infinity variable slot between the plates. In the drawings, the four parts which comprise the shutter are shown separated in Figs. 1 to 4 4 but in operation they are bolted closely together through the holes 4. The leading shutter plate 2 and following shutter plate 3 (Fig. 1) are actuated by pins 6, 20 respectively, which project through slots 22, 21 in plate 11 (Fig. 2). Pin 6 is connected to the common drive ring 13 by a toggle lever 19 and pin 20 is connected to the drive ring 13 at 16 by means of the flexible spring or rod 17 An adjustable stop 23 which has a curve 24 for accommodating the flexible rod 17, is slidable up or down .by lever 25 to set the width of the shutter aperture. The ring 13 is connected to a setting ring 34 (Fig. 3) by means of a pin 35. The shutter is set by rotating the lever 50 (Fig. 4) about its pivot 51 in a clockwise direction, whereupon it engages the pin 47 on setting ring 34 and rotates the latter against the action of driving spring 41 until the shoulder 36 engages behind the shoulder 39 of release lever 38. At the same time the coupled ring 13 rotates and pulls the plates 2 and 3 to their lowest position, the flexible member 17 bearing against the circumference of ring 13. When the release 53 is depressed, the shoulder 36 of ring 34 is released, and the drive ring 13 is rotated in an anticlockwise direction causing the toggle lever 19 to drive the lead ing plate 2 across the exposure aperture. Meanwhile the flexible rod 17 moves idly downwards until it is arrested in the curve 24 of stop 23, then, on continued rotation of the ring 13, the rod 13 drives pin 20 and thus the following plate 3 upwards. When pin 6 has reached the top of its movement, toggle lever 19 bends at joint 28, which is guided in slot 29 (Fig. 3) to allow the following plate 3 to complete its movement. The distance at which plate 3 follows plate 2 across the exposure aperture depends on the position of the adjustable stop 23. Bulb exposures are provided by setting stop 23 at its lowest position in which its end 46 (Fig. 2) becomes disengaged from the lug 45 on a latch 40, pivoted at 43 and loaded with a spring 44 (Fig. 3). The lug 45 bears against the end of release lever 38, but when this is depressed, latch 40 rotates and its stop 55 engages a projection 37 on the setting ring 34, which is thus arrested before the following plate 3 has commenced its movement. Release of the lever 38 allows the ring 13 to complete its rotation 'and move the following plate 3 across the exposure aperture.